Abstract: A duct system generally comprises a flexible duct; a fitting having an end including either an in-turned circumferential lip or a plurality of circumferentially arranged tabs; a collar having a first end and a second end, the first end being adapted to be secured to the flexible duct, and the second end being adapted to be secured to the end of the fitting, such that, if the second end of the fitting includes an in-turned circumferential lip, the second end of the collar includes a plurality of circumferentially arranged tabs adapted to engage the in-turned circumferential lip, and if the end of the fitting includes a plurality of circumferentially arranged tabs, the second end of the collar includes an in-turned circumferential lip adapted to engage the plurality of circumferentially arranged tabs; and at least one gasket for forming a seal between the fitting and the collar.